All-metal high capacity burner



Aug.26,1969 J.D.NESBITT ALL-METAL HIGH CAPACITY BURNER 'Filedilay 29, 1967 2 Sheets-Sheet 1 INVENTOR. JOHN D. lVfSB/TT w w a M I I l I I I II 3 n I I HHHHH 1 m Z l lHHHHH 8 a 2 Q I ma v l l l l lnu 2 W a, 1 u 3 4 M m Z IMP .M I I I H 7 5 l a M D w a a u a E a Q 5 6 6 6. 5 6 u 7 %J a w & fi/ 0 0 7 a 1;

BY flw attorney Aug. 26, 1969 J. o. NESBITT ALL-METAL HIGH CAPACITY BURNER 2 Sheets-Sheet 2 Filed llay 29, 1967 INVENTOR. JOHN D. IVESBITT BY w attorney United States Patent Int. Cl. F23] 9/04 U.S. Cl. 263-49 11 Claims ABSTRACT OF THE DISCLOSURE This invention relates to an all-metal, high capacity excess air burner that utilizes air to cool the burner parts, as well as combust and dilute the gas. The burner of this invention has an annular mixing and combustion chamber whose inside and outside diameter walls have radial air inlet ports through which air passes to mix with and ignite combustible gas that flows axially within the chamber. The air flowing about and through both diameter walls provides a cooling effect to these walls so that high capacity may be realized without a detrimental eifect upon the metallic components. The burner of this invention has a short flame length, which length is independent of burner capacity.

BACKGROUND In the drying of materials such as grain, chemical products, stone, sand and gravel, burners are used to heat air which is subsequently directed across the materials to be dried. In the past,- these burners have, by and large, been made with ceramic combustion tunnels'when high capacities were required. The use of ceramics was necessary as the high quantity of heat associated with the high capacity burners would have a damaging effect upon any metal components within the combustion chamber. One disadvantage of these ceramic burners was that they would tend to create cracks when in service, which cracks would adversely aflect burner operation and capacity. In addition, these ceramics would tend to dust and spall when in use and ultimately contaminate the product which was being dried.

Another disadvantage of prior burners, whether all metal or made with ceramic, was that the flame length increased as the heating capacity of the burner increased. This not only requires the use of more space, but at times -could lead to the flame inadvertently contacting the product to be dried, thereby destroying the same.

It is, therefore, the primary object of this invention to provide an all-metal burner of high capacity for use in low temperature heat processing. v

It is a further object of this invention to provide a metal burner that utilizes air as a cooling means.

It is still another object of this invention to provide a high capacity excess air burner having a short flame length.

It is a further object of this invention to provide an excess air burner having a high turn-down ratio.

It is a still further object of this invention to provide a burner having air-cooled combustion chamber Walls.

It is another object of this invention to provide a burner having a relatively short flame length, which flame length is virtually independent of burner capacity.

Further and other objects may be understood by reference to the accompanying specification, drawings and appended claims.

In the drawings:

FIG. 1 is an elevational view, in section, of a burner embodying the principles of the present invention.

FIG. 2 is a cross-sectional view taken along the lines 2-2 of FIG. 1 and FIG. 3 is a cross-sectional view taken along the lines 3--3 of FIG. 1.

SUMMARY The burner of this invention utilizes an annular combustion chamber disposed within a housing. Both the inside and outside diameter walls of the annular combustion chamber have a plurality of openings, or radial ports, therein through which air is introduced into the combustion chamber. At one end, or upstream end, of the combustion chamber, gas is introduced and flows along the length of the combustion chamber. A plurality of tangential air inlets is provided at the upstream end of the combustion chamber and a means for igniting the incoming air and gas is included. This combination results in a spinning, stable flame adjacent the gas inlet. Disposed along the length of the combustion chamber are a plurality of baflles that provide mixing of the air is entering the chamber through the radial ports, with the gas that is flowing axially along the length of the combustion chamber.

DETAILED DESCRIPTION Referring now to the drawings, a burner, or combustion apparatus, is shown generally at 10 comprising a longitudinally extending cylindrical housing 12 having a large radial opening 14 at one end thereof. A radially extending air duct 16 is received within the opening 14. The cylindrical housing '12 has a rear wall 18 attached thereto, as by not and bolt assemblies 20, and the rear wall has a central opening 22 therein through which a fuel pipe 24 is received and sealingly welded thereto. Located within the cylindrical housing 12 is a pair of concentric cylindrical wall members 26 and 28 each having a plurality of openings, or radial ports, 30 and 32, respectively, therein. The size of the openings 30 and 32 are shown out of proportion for the purpose of illustration. The perforated cylindrical walls 26 and 28 form a combustion chamber 34 therebetween and the outside cylindrical wall 26, in cooperation with the housing 12, defines an air plenum 36. The second cylindrical wall member 28 forms an inside air plenum 38.

Welded to each end of the cylindrical wall member 28 is a circular plate 40 and 42 having openings 44 and 46 therein. That portion of the fuel pipe 24 disposed within the housing 12 has four circumferentially spaced openings 48 into which are received a plurality of channel members 50 that terminate a short distance from the combustion chamber 34. Attached to the ends of the channel members 50 and extending to the combustion chamber 34 is a ring manifold 52. The ring manifold 52 has a rim 54 with a plurality of circumferentially and axially disposed openings 55 about its outside perimeter which, in cooperation with the channels 50, provide a confluent relationship between the fuel pipe 24 and the combustion chamber 34. Air inlet pipes 56 are welded to and extend from the outside perimeter of the cylindrical wall member 28 to the plenum 36, tangentially relative to the internal diameter of the combustion chamber 34, and in a spaced relationship relative to the perforated. rim 54. Welded stream end of the combustion chamber 34. This annular back plate 58 has three relatively large openings 60', 61 and 62 therein, one of which openings 60 receives a spark plug 64, another 61 a gas inlet tube 65 and the other 62 a flame detection device 66. The flame detector 66 is used to determine Whether flame exists within the combustion chamber 34 and controls a valve (not shown) in the fuel line to shut off the supply of fuel when no flame is present. The gas inlet tube 65 is received within the manifold opening 61 is proximity of the spark plug 64 and acts as a pilot which supplies sufficient gas to maintain combustion after the initial ignition. Within an opening 68 of the air housing rear wall 18, a connector 70 is provided, which connector has an electrode 72 centrally located within an insulator body 74, there being a wire 76 leading from the electrode to the spark plug 64.

A pair of annular plates 78 and 80 is welded on to each end of the air plenum 36. These annular plates 78 and 80 have a plurality of openings 82 and 84 therein, the upstream openings 82 being somewhat larger than the down stream openings 84.

Extending longitudinally within the combustion chamber '34 and attached to the inside perimeter of the outside cylindrical wall member 26 and the outside perimeter of inside cylindrical wall 28 are a plurality of baflles 86 and 88, respectively. The baflles 86 of the outside wall member 26 are staggered axially relative to the baflies 88 or the inside wall member 28.

In operation, combustible gas is supplied from the gas inlet 65 and fuel pipe 24 through the channels 50 and ring manifold 52 into the combustion chamber 34. Air is supplied initially to the air duct 16 under pressure and passes through the openings 82 of the plate 78 to enter the air plenum 36. The air also passes through the openings 44 in the circular plate 40 to enter the central air plenum 38. After the air enters the air plenum 36, a portion of it passes through the openings 30 and flows into the combustion chamber 34 and a portion of the air in the central plenum 38 flows through the openings 32 into the combustion chamber.

The two plates 40 and 78 with their respective openings 44 and 82 are included to create a pressure drop sufficient to balance air flows despite minor variations in approach velocity as the air enters the outside or inside air plenum 36 and 38, respectively. The air entering the combustion chamber 34 through the radial ports 30 and 32 should not enter under too great a pressure as this would tend to disrupt or perhaps quench the flame pattern within the chamber 34. Thus, the perforated plates 40 and 78 are provided.

A portion of the air, 2-6% of the total air, is introduced into the combustion chamber 34 through the tangential air inlets 56 to form a spinning air stream circumposing the gas that is emitted through the ring manifold 52. These tangential air inlets 56 are spaced about the ring manifold 52 with sufficient frequency and each has a length great enough to assure tangential direction of the air flow and minimize velocity decay port to port. If the tangential air inlets 56 were spaced an appreciable distance from one another and were too short, the air stream therefrom would tend to flow toward the central axis instead of tangentially. The gas is introduced from the ring manifold 52 radially so that a continuous flame is maintained from the combustion chamber back plate 58 to the first mixing baflle 86 to avoid unstable operating. The spark plug 64 is used to ignite the mixture of air coming from the tangential air inlets 56 and the gas coming from the ring manifold 52. As the fuel flows axially along the combustion chamber 34, it then mixes with air that flows through the radial ports 30 and 32 to be further combusted. Mixing of the gas and air is obtained primarily by the presence of the bafiies 86 and 88 so that a large percentage of the gas is combusted Within the combustion chamber 34. As the gas exists from the combustion chamber 34 into the atmosphere, it further reacts with the air discharged from openings 84 and 46 to obtain complete combustion in the smallest axial distance.

The burner of this invention is made from all metal components, these metal components being provided with means to keep them cool while under high capacity operations. The cooling means is provided, in part, by the openings 30, 32, 42 and 84 in the Walls and plate 26, 28, 42 and 80, respectively. The air passing through the openings 30 and 32 at relatively high velocity provides the major cooling effect to the wall members 26 and 28. In addition, the air moves along the surfaces of the wall members 26 and 28, before passing through the openings 30 and 32, to give a cooling effect to these wall members, thereby keeping them from becoming extremely hot due to the combustion that is taking place. Air passing through the openings 46 and 84 of the plates 42 and 80, respectively, not only cools by flowing thereby, but also prevents the flame issuing from the combustion chamber 34 from contacting these plates. The burner 10 is cooled to such an extent that it can be mounted within a metal duct or air heater wall with assurance of no overheating of such ducts or walls.

In addition to providing an all-metal high capacity excess air burner, the burner 10 of this invention has other important advantages. A favorable feature of the burner 10 is that a high tum-down ratio is achieved. As the fuel is introduced into the fuel chamber 34 through the ring manifold 52, it will be burning when at maximum capacity, along the entire length of the fuel chamber. As the amount of fuel to the combustion chamber 34 is decreased, the combustion taking place in the chamber, that is the burning fuel and air, recedes inwardly or upstream so that only a portion of the combustion chamber has combusting gases therein. As the burning recedes into the combustion chamber, the proper ratio of air to fuel is maintained since the number of radial air ports decreases in proportion to the length of the combusting fuel. Thus, the flame will not be quenched by excess air.

In addition to the high turn-down ratio, this burner has the added advantage of having a short flame length, which flame length is virtually independent of burner size or capacity. Because of the short flame length, the burner 10 is able to concentrate its heat in a smaller area, not to mention that the amount of room needed to carry out its operation is substantially reduced. For example, a 20 million B.t.u.s per hour burner having an outside diameter of 2 /3 ft. will have a flame length of approximately 6 feet when operated at full capacity. The flame length is virtually independent of burner size or capacity because the width, or radial length, of the annular combustion chamber 34 is maintained constant. The capacity of the burner 10 is a function of the square of the diameter, but the length of the flame is determined by the width of the combustion chamber or annulus 34. Since the diameter may be varied to increase the capacity and the combustion annulus may be kept constant, no flame length change will result from increased burner capacity.

Although only a single embodiment of this invention has been shown and described, it is understood that changes and modifications can be made therein, and this description is illustrative only and not for the purpose of rendering this invention limited to the details illustrated or described except as they are limited by the terms of the following claims.

I claim:

1. A combustion apparatus comprising: wall means forming a generally cylindrical duct, a first perforated, cylindrical member disposed Within said duct and defining a channel therebetween, a second perforated cylindrical member disposed within said first member to define a chamber therebetween, means at one end of said wall means for supplying air to the channel and to the second member, means for supplying combustible gas to the chamber at said one' end, a plurality of axially spaced baflles disposed within said chamber and secured to at least one of said cylindrical members, and ignition means within said chamber at said one end, whereby air flows through the perforations in said first and second cylindrical members to mix with said gas, and said ignition means combusts the resulting mixture.

2. A combustion apparatus comprising: a longitudinally extending cylindrical wall meaus forming a housing with an open, or downstream, end; a first perforated, cylindrical member disposed within said housing and defining a plenum therebetween, the downstream end of said first member being in general vertical alignment to the downstream end of said housing; a second perforated cylindrical member disposed within said first member to define a chamber therebetween; wall means enclosing the downstream end of said second member; means for supplying air under pressure to said plenum and to said second cylindrical member; means for balancing the supply of air to said plenum and to said second cylindrical member; means for supplying combustible gas to the upstream end of said chamber; and ignition means located Within said chamber at the upstream end thereof.

3. The combustion apparatus of claim 2 wherein said wall means enclosing said second member has a plurality of openings therein, and an annular plate having a plurality of openings therein is located at the downstream end of said plenum and extending from said first member to said housing.

4. The combustion apparatus of claim 2 including a plurality of axially spaced bafiles disposed within said chamber and secured to at least one of said cylindrical members.

5. A combustion appartus comprising: a longitudinally extending wall means forming a housing with an open, or downstream, end; a first, perforated cylindrical member disposed within said housing and defining a plenum therebetween, the downstream end of said first member being in general vertical alignment with the downstream end of said housing; a second, perforated cylindrical member disposed concentrically within said first member to define a combustion chamber therebetween; circumferentially spaced air pipes received within perforations in the upstream end of said first member and extending into said plenum, said pipes extending tangentially relative to the inside surface of said first member; means for supplying air to said plenum and said second cylindrical member; means for supplying fuel to the upstream end of said combustion chamber; and means for igniting fuel and air at the upstream end of said combustion chamber.

6. The combustion apparatus of claim 5 including a plurality of axially spaced bafiles secured to the inner surface of said first member and to the outer surface of said second member.

7. A combustion apparatus comprising: wall means forming a generally cylindrical housing having a radial opening at a first, or upstream, end thereof; and air duct received within said housing opening; a backplate secured to the upstream end of said housing and having a central opening therein; a first, perforated cylindrical member disposed within said housing and having its downstream end in vertical alignment with the downstream end of said housing, said first member extending into said housing a portion of the length thereof to define an air plenum therebetween; a second, perforated cylindrical member extending into said first member to define a combustion chamber therebetween and having one end in general vertical alignment with said downstream end of said first member; wall means enclosing the upstream end of said combustion chamber; circumferentially spaced air pipes secured to the upstream end of said first member and extending into said plenum to provide an air passageway between said plenum and said chamber, said pipes extending tangentially relative to the inside surface of said first member; a ring manifold secured. to the upstream end of said second member and having a plurality of perforations about the outside perimeter and a plurality of openings in the inside perimeter thereof; a fuel pipe disposed within said central opening of said packplate and having a plurality of radially extending openings in the portion disposed within said housing; channel members received within said fuel pipe openings and extending to said ring manifold openings thereby providing a confluent relationship between said manifold and said fuel pipe; and means for igniting fuel and air at the upstream end of said combustion chamber.

8. The apparatus of claim 7 wherein said second cylindrical member has perforated plates secured to each end thereof, and said plenum is enclosed at each end thereof by a pair of perforated annular members.

9. The apparatus of claim 7 wherein said first cylindrical member has a first plurality of axially spaced baflles secured to the inside perimeter thereof.

10. The apparatus of claim 9 wherein said second cylindrical member has a second plurality of axially spaced baffles secured to the outside perimeter thereof.

11. The apparatus of claim 10 wherein the bafiles of said first plurality baffles are staggered relative to the bafiles of said second plurality of baffles.

References Cited UNITED STATES PATENTS 2,513,682 7/ 1950 Laborde et a1 431-201 2,411,342 11/1946 Sherman. 2,654,219 10/1953 Zaba. 3,368,604 2/1968 Mutchler 158-4 EDWARD G. FAVORS, Primary Examiner U.S. Cl. X.R. 43 1-352 

